By Dr. Hafsa Rais
Abstract:
Background:
This study evaluated incidental radiation dose to
the left anterior descending artery(LAD) and left ventricle as
organ at risk (OARs) in left sided breast cancer patients who
received adjuvant radiotherapy with Intensity modulated
radition therapy ( IMRT) treatment plan.RT-associated cardiac
changes are more common in left-sided breast cancer.
Materials and Methods:
Twenty-four mastectomy patients
who previously treated with IMRT were analyzed
retrospectively. LV and LAD , not initially contuored as OARs, were delineated on the same simulation CTs for those patients
whose treatment was previously completed with IMRT plans .
New intensity modulated radiation therapy (IMRT) plans were
generated,maintaining original parameters. Planning target
volume (PTV), homogeneity index (HI) , conformity index(CI)
,monitor unit(MU) values, and doses of OARs compared using
wilcoxon signed-rank test (p<0.05).
Results:
There were no clinically significant differences in PTV40
coverage (D98, D50, and D2) between the non-optimized and
optimized plans. Optimization significantly reduced cardiac
substructure doses. The mean LAD dose decreased from 27.8
Gy to 24.0 Gy (p = 0.016), and maximum LAD dose decreased
from 42.6 Gy to 37.4 Gy (p = 0.016). For the LV, the mean dose
was reduced from 13.3 Gy to 11.7 Gy (p = 0.016), and
maximum dose from 42.3 Gy to 37.9 Gy (p = 0.016). Overall,
optimization yielded a 12–14% dose reduction for the LAD and
10–12% for the LV, without compromising target coverage.
Conclusion:
In left-sided breast radiotherapy, contouring LAD and LV as
OARs provides significant dose reductions of about 10–14%
without compromising target coverage. Left-sided RT patients
had higher cardiac morbidity, mainly ischemic heart disease
(Myocardial infarction and angina), with a 0.4% excess MI
risk versus right-sided RT. LAD damage contributes to both
non-radiation and radiation-induced MI. RTinduced cardiac
injury appears decades later, requiring long follow-up